Metallic powder and method of making



Patented Aug. 1 1932 UNITED STATES PATENT OFFICE JOHN A. GAIN'N, OF MIDLAND, MICHIGAN, ASSIGNOR TO THE DOW CHEMICAL COMDANY, OF MIDLAND, MICHIGAN, A CORPORATION OF MICHIGAN METAL L1G POWDER AND METHOD OF MAKING Io Drawing.

The present invention relates to light metal alloys and in particular to brittle alloys containing magnesium. Alloys of this type have utility in a number of fields, for instance, in pyrotechnics in general and as deoxidizers and alloying materials.

Heretofore when makingmetallic powder containing two or more of the metals magnesium, aluminum, copper or zinc, considerable difliculty has been encountered due to difiiculty attendant with grinding or pulverizing these materials. The difliculty of production of these metals in powdered form has made the use of special pulverizing machinery necessary for the attainment of satisfactory production and has resulted in a comparatively high priced product as compared with the cost of the metal before grindlIl have discovered that when magnesium is alloyed with the embrittling metals aluminum, copper or zinc, in binary or other forms, there is a range of composition wherein they are exceedingly brittle and may be pulverized at ease with greatly diminished expense.

One of the objects "of my invention is to provide an alloy that has a sufficient degree of brittleness to render it easily pulverizable. Other objects and advantages will appear as the description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, consists of the methods and product hereinafter fully described and particularly pointed out in the claims, the following description setting forth in detail several forms of product and modes of carrying out the invention, such disclosed forms and modes illustrating, however, but several of the various Ways in which the rinciple of the invention may be used.

hen magnesium is alloyed with the embrittling metals, aluminum, copper, zinc or combinations of these, there is in eaeh case a range of composition wherein they are exceedingly brittle. The brittle magnesium 1929. Serial No. 356,611.

containing alloy, for instance, is fragile and has a glass-like brittleness that will permit it to be easily pulverized with an ordinary mortar and pestle. The easily pulverizable range of the binary magnesium containing alloys is o as follows Magnesinm-alnminum alloy containing 30 to per cent. aluminum.

Magnesium-copper alloy containing 40 to 90 per cent. i dghesium-zinc alloy containing 40 to 80 per cent. zinc.

With reference to the above table, it is to be noted that there is not an abrupt change from the brittle range noted to the nonbrittle state but rather a gradual tapering in the degree of brittlencs as the percentage of 60 the predominating metal is further increased. The magnesium alloys in which the copper or zinc is present in the maximum amount noted above, do tend, however, to become less brittle as the percentage of the predominating metal is increased. It will, of course, be well understood by those familiar with. the art that some types of pulverizing machines will be better adapted to pulverize these alloys and will accordingly increase the readily pulverizable range.

When making a brittle alloy of magnesium with two or more of the embrittling metals aluminum, copper, Zinc, l have foundthat the range of the sum total of such embrittling metal added to the magnesium will not be greatly diiferent from the range of any one of the added component embrittling metals as shown in the table above.

In case a metallic powder mixture should be desired wherein the percentage of the constituent metals was different from the proportions lying in the extremely brittle range I would still be able to take advantage of the ease and cheapness with which the brittle alloys can be pulverized. This I would accomplish, where the properties of the final product permitted, by pulverizing a brittle alloy having the composition near to that desired, and to the so prepared powder I would add enough of the more diflicultly powdered pure metal to produce the desired mixture. The pure metal could, of course, be added in suitable form to the brittle alloy as it passes to the pulverizer without departing from the spirit of my invention. Another way that the desired mixture could be ob tained would be to make an alloy of the metals in question and then pulverize it. The pulverization of such alloy would be harder than that of the extremely brittle alloy, but, on the other hand, it would be easier to pulverize than the virgin metals. However, the particular method used for obtaining the pulverized product would, in general, be dependent upon the ultimate comparative cost and the properties desired.

The pulverizing of brittle metals and alloys in air is attended with somewhat greater combustion hazards than is normally encountered when pulverizing relatively malleable metals. However, the combustion hazard when pulverizing such brittle metals in air may be greatly diminished by adding a small percentage of other suitable material thereto as it passes through the pulverizer,

such added material being preferably a rela tively malleable metal. For instance, when pulverizing a brittle magnesium-aluminum alloy, I prefer to add thereto a small percentage, normally less than 10 per cent of powdered aluminum in polished flake form so that it will pass in approximately uniform manner through the pulverizer along with the brittle alloy. In like manner the polished aluminum flakes could be used with other brittle alloy compositions, it of course being kept in mind that where a special composition is desired without contamination with other materials, diiferent steps would have to be taken. For instance, if a magnesium-copper powder were desired copper powder could be added to the brittle magnesium-copper alloy passing through the pulverizer so as to attain the desired uncontaminated final product. In someinstances it might be advisable to do the pulverizing in aventilated hammer mill or in a pulverizer adapted to use a suitable diluent in liquid form or otherwise in order to accomplish the desired end without unnecessar danger, all of such equivalent variations eing understood to fall within the scope of my invention.

While my brittle alloy may be made by several different commercial methods I prefer to make it by first melting the magnesium in a pot containing a suitable flux bath. One such flux which has been found to work successfully in commercial practice consists of a mixture of magnesium and sodium chlorides in approximately equal proportions. Having completed melting the magnesium in the flux bath, it is then ready to be alloyed with aluminum, copper, zinc or mixtures of these. While the alloying may be accomplished in several ways I prefer to "do it with a ladle. The method of doing this can be best explained by a specific example, for instance, the method of alloying magnesium and copper. When alloying this metal with magnesium I prefer to dip a small quantity of the molten metal from the pot with a ladle and add the copper thereto in suitably sized pieces. Upon then stirring up the metal in the ladle the copper will gradually dissolve in the magnesium. The molten contents of the ladle are then poured back into the main body of the metal and a further quantity of the latter dipped into the ladle and stirred with the copper as before, this operation being continued until the amount of copper in the mixture in the pot equals that called for by the formula.

For the purpose of definition the expression embrittling metal or metals, shall in the absence of other generic terms be understood to refer to one or more of the metals aluminum, copper or zinc.

Other modes of applying the principle of my invention may be employed instead of those explained, change being made as regards the methods and materials employed, provided the methods or'ingredients stated by any of the following claims or the equivalent be employed.

I therefore particularly point out and distinctly claim as my invention 1. A method of making a metallic powder, which comprises simultaneously passing a brittle magnesium-aluminum alloy and polished flake aluminum through a pulverizing zone.

2. A metallic powder consisting of a pulverized -mixture of brittle magnesium-aluminum alloy and polished flake aluminum.

3. A method of making a metallic powder which comprises simultaneously passing a brittle magnesium alloy and finely divided metal of the same kind as alloyed with the magnesium, through a pulverizing zone.

4. A method of making a metallic powder which comprises simultaneously passing a brittle magnesium alloy and polished flake aluminum through a pulverizing zone.

5. A metallic powder comprising a mixture of a pulverized brittle magnesium alloy and a finely divided metal of the same kind as alloyed with the magnesium, wherein the brittle magnesium alloy is present in predominating amount and the metal of the same kind as alloyed with the magnesium is present in amount up to approximately 10 per cent.

6. A metallic powder consisting of a pulverized mixture of brittle magnesium-aluminum alloy and up to 10 per cent of polished flake aluminum. I

7. A method of making a metallic powder which comprises pulverizing a brittle magnesium alloy in the presence of a finely divided metal selected from the group consisting of aluminum, copper and zinc.

8. A metallic powder consisting of a pulverized brittle magnesium alloy intimately mixed with a relatively small percentage of a finely divided metal selected from the group conslsting of aluminum, copper and zinc.

Signed by me this 16 day of April, 1929.

JOHN A. GANN. 

